London: A new math method can help predict a woman's chances of becoming pregnant, depending on how long the couple has been trying, say researchers.For instance, the researchers from Warwick Medical School found that, if the woman is aged 35 years, after just six months of trying, her chance of getting pregnant in the next cycle is less than 10 percent.

The analysis, developed by Warwick Medical School and the London School of Economics, uses the number of menstrual cycles over which the couple has been trying for a baby to determine a probability of conception within the next month, the journal Public Library of Science ONE reported.

The method makes use of an important math result first described by Thomas Bayes, an 18th century Presbyterian minister, which allows probabilities to be calculated by combining prior information with new evidence, according to a Warwick statement.

Peter Sozou of the London School of Economics said: "After several cycles without pregnancy, it becomes relatively more likely that a couple have low fertility.

"This is the main reason why it becomes less likely that conception will occur in the next cycle."Geraldine Hartshorne, professor at Warwick Medical School, added: "Many couples are not aware that chance plays a big role in getting pregnant. People expect to get pregnant when they want to, so finding out that it isn't happening can be a shock.

"Approaching a doctor about such a personal matter is daunting so knowing when is the right time to start investigations would be a useful step forward," said Hartstone.

"We can't work out exactly when, or if, a woman will become pregnant - but this analysis can predict her chances, and give a percentage estimate of pregnancy in the next cycle," concluded Hartstone.